The present invention relates to a magnetic trip for an electrical switching device, comprising a fixed magnetic circuit which is in association with a permanent magnet, at least one coil able to be passed through by an electric current and in association with a circuit branch to determine a magnetic flow which is function of the current, and a moveable pallet acted upon by a spring and determining with the fixed magnetic circuit a main flow loop.
It is important to be able to manufacture such a magnetic trip so that its pallet activates the trip mechanism of the device as rapidly as possible, for example in a few tenths of a millisecond, in response to excess current in the coil. It is moreover desirable for the magnetic flow induced by the excess current not to lead to demagnetisation of the permanent magnet.
The purpose of the invention is to make highly reactive a trip of the type described and to simplify its manufacture.
According to the invention, the magnetic circuit includes, near the magnet, at least one magnetic flow deflection tab defining a secondary flow loop equipped with at least one secondary air gap, and the tab is arranged relative to the fixed magnetic circuit and to the magnet so that an excess current in the coil deflects the flow of the magnet to the secondary loop.
Preferably, the magnetic circuit includes two identical parallel wafers each having on the one hand a main branch carrying a coil and on the other hand a deflection tab, the free ends of the tabs defining two secondary transverse air gaps, and the magnet is placed between the wafers near the tabs.
Each coil may be wound onto a U-shaped insulation half-shell enclosing by the wings of the U the small sides of the corresponding wafer, with the result that the coil is immediately adjacent to a lateral face of the wafer, the half-shells being assembled so as to form an insulation structure carrying the coils and containing the wafers.